Experimenting with the Hackrf

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Experimenting with the Hackrf

The Hackrf is a small affordable SDR (software Defined Radio) that can operate in frequencies up to 6GHz with a channel bandwidth of 20MHz. This makes it an excellent choice when it comes to experimenting with WiFi. One of the few drawback of a Hckrf is the lack of amplification on the Tx side. In this experiment I was successful in amplifying the transmit signal of a Hackrf by 30dB using a Skyworks FEM ( Front-End Module).

GNU radio is used to generate an 64 tone OFDM signal which is forwarded to the Hackrf. I will be writing a detailed post on how to replicate this experiment in the future. For now I would like to share with my readers short videos showing the difference in Tx power with and without the a FEM.

Without a FEM, received signal level from the Hackrf is around -60dBm

With a FEM, received signal level from the Hackrf is around -30dBm

4 Comments

Diogo Dias Posted on 10:08 am - November 9, 2020

Hello. Good morning. Can I ask you a question about your experiment? I’m really noob in all this, a little fish in a very large tank, your results in the 5ghz range are very promising but I must ask this type of FEM are any different from a standard LNA? Is this better than a standard LNA? I’m asking cause I’m preparing my hackrf to do WIFI testing and the TX is very poor over 5ghz and I’m exploring some ideas to boost it, I found some LNA that covers the full HackRF range but the boost level over 5ghz are a bit worse than you showed. I would be very thankful if you could shed some light on this. But awesome experiment keep going and have a nice day.

Reply
    firas.shaari Posted on 1:05 pm - November 9, 2020

    LNA stands for low noise amplifier and its usually used on the Rx side.PA stands for power amplifier and is used to amplify the Tx signal. In this experiment I was using the PA to amplify the Tx signal. The FEM had both a PA and an LNA and control pins to switch either of them on or off. All I did was supplying voltage to the VCC and the PA/ENABLE pins on the FEM to amplify the Tx signal only. Here is a good link explaining the concepts of PAs and LNAs in more details.
    https://electronics.stackexchange.com/questions/237267/what-is-a-pa-lna/237269

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